Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CARNITINE SUPPLEMENTED DIET TO PREVENT
OR ALLEVIATE ASCITES IN BROILER TYPE POULTRY
BACKGROUND OF THE INVENTION
1. Field of Invention:
The present invention relates generally to disease prevention in livestock,
and, more
specifically, to the prevention or alleviation of ascites in broiler type
poultry.
2. Background:
Ascites, also known as pulmonary hypertension syndrome, is a condition
characterized by
the accumulation of serous fluid in the spaces between tissues and organs in
the abdominal cavity
and is most prevalent as an affliction of poultry. The fluid is clear or amber
in color, originates
from the liver and has the general composition of plasma. Also referred to as
waterbelly, high
altitude disease and avian edema, ascites is attributable to the inability of
the cardiovascular
system to meet tissue oxygen demands.
The economic consequences associated with ascites are severe and occur due to
a
combination of increased bird mortality and condemnations along with reduced
growth rate and
feed efficiency. In the United States alone, annual poultry industry losses
due to ascites are
estimated to exceed 65 million dollars. Though estimates for dollar losses in
other countries are
not as readily available, the annual global impact of this disease likely
exceeds a billion dollars.
In most cases ascites is brought about by a divergent bird oxygen requirement
and its
cardiovascular ability to supply oxygen as a nutrient. The inability of the
cardiovascular system to
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meet tissue oxygen demands may result from may different circumstances, one
example of which
is a reduced atmospheric oxygen concentration. It was under these conditions
in the 1970's that
ascites was first recognized as a disease in broiler flocks grown at high
altitude in South Africa
and South America. Birds initially compensate for reduced tissue oxygen supply
by increasing
cardiac output. However, problems arise when the return blood volume exceeds
the capacity of
the heart to pump the blood. As a result, the heart enlarges, becomes round in
outline and
develops a dilated right ventricle. The right heart failure causes increased
vena cava pressure and
liver congestion. Classic ascites ensues due to the increased hepatic
hydrostatic pressure resulting
in transudation of fluid through the liver capsule into the abdominal cavity.
The chronically
elevated intrahepatic pressure leads to loss of hepatic parenchyma,
intrahepatic fibrosis (cirrhosis)
and hepatic dysfunction.
Other factors contributing or predisposing poultry to ascites have been
identified.
Pulmonary tissue damage, such as caused by exposure of birds to dust and
ammonia, as well as
diseases affecting the lungs (e.g., infectious bronchitis, Newcastle disease,
infectious coryza,
colibacillosis, aspergillosis), is known to be associated with an increased
incidence of ascites, as is
reduced cardiac function. Excess furazolidone, toxic fat and excess salt in
the diet are also
predisposing factors, along with cold distress brought about by nonevaporative
heat loss.
Despite a better understanding of the disease, there has been a dramatic rise
in ascites
incidence in recent years. Primarily responsible is the increased growth rate
of today's genetically
engineered birds. The desire to achieve rapidly growing lean strains of meat
chickens and the
demands from processors to increase yields by reducing the overall size of
visceral organs has
meant a selection of strains susceptible to ascites. To put it in perspective,
the age to slaughter
and the amount of feed required to produce a given quantity of chicken meat
has been more than
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halved since the early 1950's. See Havenstein, G.B,, P.R. Ferket, S.E.
Scheldeler and B.T.
Larson, Grou,th, Livability a d Feed Conversion of 1957 vs. 1991 Broilers
Wheir Fed "7ypical "
1957 and 1991 Broiler Diets, Poriltiy Science, Vol. 73, pp. 1785-1794 (1994).
In the early
1950's the average length of time required to grow a broiler chicken to a 4
pound harvest weight
exceeded 15 weeks. Through genetic selection, this time period has been
reduced to a current
average of about 6 weeks. Consequently, bird metabolic events that are needed
to produce a unit
of poultry meat have been squeezed into a shorter time period, creating a high
metabolic demand
in today's bird. Such metabolic demand is further elevated by environmental
factors, such as low
and high ambient temperature, and disease. As a bird having a high metabolic
demand possesses a
higher oxygen requirement, severe stress is placed on the bird's
cardiovascular support system.
The stress is exacerbated when gain composition consists primarily of protein
gain, as is the case
with broiler type birds. Studies by the inventors show that trial broilers
consumed 3.1 liters of
oxygen per gram of protein gain versus just .82 liters of oxygen per gram of
fat over a 35 day
production period. Thus, a bird's ability to consume and transport oxygen not
only has the
potential to impact bird health via ascites, but also carcass composition by
limiting protein
synthesis ability.
The incidence of ascites in fast growing birds may be reduced by lowering gain
accretion
rate, such as by feeding low caloric density rations and restricting feed
intake; however, lowering
growth rate is not appealing to the poultry industry as it fails to maximize
bird productivity.
There is thus a need for an aid to prevent or alleviate ascites in stressed,
rapidly growing
livestock, particularly poultry. The present inventors have discovered such an
aid in a carnitine
supplemented diet for poultry. The diet is unexpectedly effective at reducing
the incidence of
ascites (as evidenced in a reduced hematocrit, right ventricle weight and
ascites heart ratio) in
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broiler type poultry and potentially enhances growth rate, feed efficiency,
survivability and carcass
quality.
In the patent art, U.S. Patent No. 5,213,815 discloses a method of treating
ascites
comprising the administration of Eyebright herb and Brewer's yeast to poultry
in need thereof.
In U.S. Patent No. 4,970,080, ascites is purportedly treated by feeding small
amounts of zeolite to
the affected animal.
Heretofore, carnitine in poultry diet has been reported to have no beneficial
effect on feed
intake, body and abdominal fat weight or on carcass or liver lipid levels in
growing broilers
(Cartwright, Po7rltiy Science, Vol. 65, Suppl. 1, p. 21, 1986). Dietary
carnitine has been shown
to retard ethanol metabolism in broilers (Smith et al., Poziltiy Science, Vol.
71, Suppl. 1, p. 64,
1992), and, in U.S. Patent No. 5,362,753, to increase the hatchability of
eggs.
Unrelated to poultry, carnitine has been used as a supplement in pig diets
(U.S. Patent
Nos. 5,124,357 and 5,192,804 and PCT Publication WO 98/24328), a smolting feed
for salmon
(U.S. Patent No. 5,722,346) and in a catfish diet (U.S. Patent No. 5,030,657).
The use of
carnitine in the treatment of heart failure or myocardial ischemia is
discussed in U.S. Patent No.
4,075,352 and PCT Publication WO 98/43617.
Notwithstanding the known uses of carnitine, the prior art wholly fails to
teach or suggest
as disclosed and claimed herein a carnitine supplemented diet fed to broiler
type poultry to
prevent or alleviate ascites.
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BRIEF SUMMARY OF THE INVENTION
According to an aspect of the present invention, there is provided use of a
feed
composition for the preparation of a veterinary medicine for preventing or
alleviating ascites
5 in poultry, wherein said composition consists essentially of a basal diet
and carnitine.
According to a further aspect of the present invention, there is provided use
of a
solution for the preparation of a veterinary medicine for preventing or
alleviating ascites in
poultry, wherein said solution consists essentially of camitine and water.
In connection with the present invention, an effective amount of carnitine is
administered
to broiler type poultry to prevent or alleviate ascites. Preferably, L-
carnitine is administered as a
supplement to the birds' food or water supply. Application in a feed
composition is most
preferred, wherein the amount of L-carnitine provided is between 5 to 1000
parts per million
(ppm), and most preferably about 10-400 ppm, of the feed composition.
In another aspect of the invention, the carnitine supplemented diet is fed to
broiler
type poultry between 0 and 18 weeks of age during the early life phase of
rapid tissue accretion
where a high oxygen requirement stresses the birds' cardiovascular support
system.
In a particularly preferred aspect of the invention the carnitine supplemented
diet is fed to
broiler type chickens. In this respect, the carnitine supplemented diet is
provided to broiler
chickens between 0 and 11 weeks of age that have a live weight of up to 12
pounds, and, most
preferably, to broiler type chickens between 0 and 7 weeks of as"e and
weighing up to 7 pounds.
While these parameters represent the current best mode and preferred
embodiment for carrying
out the present invention, it should be understood that because poultry
industry goals focus on a
one-tenth pound per year increase in bird weight, the years to come may see
even greater bird
growth rates and harvest weights.
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A better understanding of the present invention and its objects and advantages
will become
apparent to those skilled in this art from the following detailed description,
wherein there is
described only the preferred embodiment of the invention, simply by way of
illustration of the best
mode contemplated for carrying out the invention. As will be realized, the
invention is capable of
modifications in various obvious respects, all without departiny, from the
scope and spirit of the
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invention. Accordingly, the description should be regarded as illustrative in
nature and not as
restrictive.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Carnitine, chemically known as 3-hydroxy-4-N-trimethylaminobutyric acid or,
alternatively, -hydroxy- -trimethylaminobutyric acid, is a quaternary ammonium
compound
present in vertebrate muscle whose metabolic function involves the transfer of
fatty acids across
mitochondrial membranes. Like many other biological molecules, carnitine comes
in two forms:
L-carnitine and D-carnitine. As used herein the term "carnitine" refers to L-
carnitine and/or
pharmaceutically acceptable non-toxic salts thereof, non-limiting examples of
which are tartrate,
fumerate and magnesium citrate.
The preferred embodiment of the present invention involves the use of
carnitine as a
dietary supplement in broiler type poultry experiencing a high metabolic
demand for energy due to
high rate tissue accretion to prevent or alleviate ascites. The term "poultry"
is used herein in its
normal broad sense, referring to birds of several species, including chickens,
turkeys, ducks,
geese, swans, guineas, pigeons, peafowl, ostriches, pheasants, quail and other
game birds. The
term "broiler" refers to a subset of each species of poultry consisting of
meat-type birds (i.e., birds
produced for human consumption), 'well known in the industry, of an age
generally between 0-18
weeks, depending upon the species of bird. Turkeys, for example, are generally
grown to an older
age than chickens. The inventors have surprisingly discovered that a carnitine
supplemented diet
fed to broiler type poultry during periods of high metabolic stress where the
bird's oxygen
requirement is elevated reduces the incidence of ascites as reflected in
decreased values in bird
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hematocrit, right ventricle weight and ascites heart ratio. The theorized mode
of action is the
enhancement of lipid energy utilization within the heart for the tyeneration
of ATP and enhanced
cardiac contractile function. Feeding the inventive diet should enhance feed
efficiency and bird
survivability while reducing condemnations within the processing plant.
The present invention is particularly suitable for use with all young meat-
type chickens.
Broiler chickens are generally marketed at 5-7 weeks of age at a live weight
of 4-7 pounds,
although some, sometimes called "roaster" chickens, are marketed at 8-11 weeks
of age at live
weights between 7 and 12 pounds. For purposes of this application, however,
all meat-type
chickens are encompassed within the generic term "broilers" defined above. The
term also
encompasses poultry specialty products, such as so-called "Cornish hens,"
harvested at about 18
days of age at a weight of 1-1.5 pounds. From the time of hatch until harvest,
these birds have a
metabolizable energy requirement (from 2700-3300 kcal/kg ration) and
concomitant oxygen
demand that, in many cases, exceeds the capacity of the bird's cardiovascular
system. Birds
whose cardiovascular systems cannot handle the increased oxygen requirement
brought on by
rapid tissue accretion in this growth phase of the life cycle are prone to
contract the ascites
condition. Providing birds with a carnitine supplemented diet during this
period of high metabolic
demand has been shown to reduce the ascites incidence by lowering right
ventricular weight and
the ascites heart ratio, a known indicator for ascites susceptibility, and to
also lower blood
hematocrit, a variable that is correlated with ascites occurrence.
In connection with the present invention, supplemental carnitine is provided
to broiler type
poultry in a prophylactic or therapeutically effective amount, where the
desired effect is a
decrease in the incidence of ascites. This decrease can be of any level below
the disease incidence
of broiler type poultry fed a diet without the carnitine supplement.
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It is preferred that the supplemental carnitine be provided in the diet of
broiler type
poultry, in either solid or liquid form, and, most preferably, as part of a
feed composition. The
necessary concentration of carnitine for a particular species and breed of
poultry being fed may be
optimized by one of ordinary skill by testing a range of carnitine
concentrations using trial feed
compositions. In the case of broiler chickens, an effective amount of
carnitine will range from
about 5 ppm of the feed composition upwards. While no upper limit has been
established as being
counterproductive to the aims of the present invention (for convenience an
upper range of 1000
ppm is suggested), the best known mode to practice the invention currently
contemplates feeding
a carnitine supplemented diet to broiler type chickens wherein the effective
amount of carnitine is
from about 10 ppm to about 400 ppm of the feed composition, and, most
preferably, about 40
ppm of the feed composition.
The basal diet to which the carnitine is added can be any typical poultry diet
meeting the
nutritive needs of the broiler type bird, including starter, grower and
finishing rations. A
conventional diet includes selections among various protein, carbohydrate,
vitamin and mineral
sources and will generally contain about 12-25% crude protein, 0.5-10% crude
fat and 2-12%
crude fiber. The primary component is generally grain and processed grain by-
products which
supply carbohydrates and some protein. Protein meals from soybeans, alfalfa,
corn gluten,
cottonseed, sunflowers and other plants are often used to supply additional
protein to the diet, as
are animal by-products. Poultry feed compositions are generally supplemented
with various
vitamins and minerals, and molasses and animal fats are added to improve
palatability and to
increase or balance energy levels. General reference is made to National
Research Council,
Nrilr-ienl Requn-emenis qf Pvrrltiy, Nirh7G'ni Reqlnl-Bndenls of Domestic
Aninial.s. National
Academy of Science, Washington, U.C. (1994), for a discussion of poultry
nutrient requirements
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and typical poultry rations for various species and life phases of poultry.
Typical rations are
also given below in connection with the reported examples. The feed schedule
and feed rates
can also be any standard schedule and rate used in the art.
As carnitine is water soluble, it alternatively may be administered through
the bird's water
supply. However, as water consumption varies according to the type of feed
consumed,
temperature, humidity, and activity of the bird, intake must be carefully
monitored. The ratio of
water to feed consumption in chickens generally ran~es from 1.5-3.0 to 1, but
may exceed 4-1
duritig high ambient temperature exposure or during periods of prolonged
stress.
The present invention will be fi:rther understood by referetice to the
following non-limiting
example.
EXANiPLE
Matc.~rials crnd Methocls; Male Cobb-500 broiler chicks (obtained from Cobb
Vantress of
Siloam Springs, Arkansas) were used. The chicks were divided into 24 groups of
4 and 24 groups
of 9 chicks and randornly assigned to 60 open circuit respiratory chambers in
three separate
rooms. The chambers were housed in 3 thermostatically controlled rooms with 24
hour
fluorescent ligllt. Two levels of carnitine (0,200 pptn) were added to the
basal diets (Table 1) and
examined at two oxygen levels (17 and 20.6%).
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Table 1. Composition of Basal Diets
Ingredients Basall Basal 2 Basal 3 Basal 4
Corn/grd 56.51 46.51 63.52 5154
Soybean meal/sol 34-40 34.59 31.96 36.32
Vegetable oil 3.54 3.11 0.54 0.74
Dicalcium 1.67 1.68 1.66 1.67
phosphate
Limestone 1.40 1.42 1.41 1.41
Salt 0.42 0.43 0.41 0.41
Vit mix' 0.20 0.20 0.20 0.20
Trace mineral mix2 0.11 0.11 0.11 0.11
DL-Methionine 0.16 0.10 0.20 0.06
(99%)
Corn gluten meal 1.58 11.85 -- 6.53
ME(kcal/kg) 2785.9 2806 2591.4 2606.5
CP% 19.9 24.8 18.53 23.06
5 ~ Mix supplied the following per lb: Vit A. 9.200.000IU; Vit. D3.
2.800.000IU; Vit. E, 21,700IU; Vit. K.
2.600mg; Thiamine, 2,000mg; Riboflavin. 7,000mg; Niacin, 54,700mg: Pantothcnic
Acid, 11.300mg;
Pyradoxine, 3.400mg; Vit. B 12. 15.1 mg; Folic Acid, 967mg; Biotin, 1 I 5mg.
2 Mix supplied the following per kilogram: Manganese, 120mg; Zinc, 100mg;
Copper, 10mg; Iodine.
10 2.5mg; Calcium, 135mg; Iron. 75mg; Selenium, 0.15mg.
Feed and drinking water were provided for acl-IiGiluni consumption. Chamber
temperature was maintained at 30 C the first 5 days of age and at 27.8 C
thereafter. Chambers
were checked twice daily for bird mortality. Body weights of each chick were
obtained on day 0,
7 and 14. Feed consumption was determined on a chamber basis at the end of 1
and 2 weeks and
feed efficiency calculated. Oxygen consumption and CO2 production was recorded
continuously
on all chambers. Five birds at the start of the experiment were sacrificed for
determination of
initial composition. At the end of the experiment (Week 2) blood samples were
taken from the
wing vain of all birds for hematocrit determination. Heart weight and right
ventricular mass of
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each bird were measured and the carcass saved for determination of lean and
fat tissue gain usin~g
a Hologic densitometer.
Breathing Air Supply and Atlalysis: Compressed dried air (7 % relative
humidity (RH),
20.6 % 02) was delivered to chicks in the chamber via polyethylene tubes. It
was necessary to
provide low RH air to the chick chamber in order to hold the chamber at RH
below 75 %. The
concentration of 02 and CO2 in air exiting each bird's chamber was monitored
each day using
Ametek oxygen (accuracy t.02%) and carbon dioxide (accuracy .03%) analyzers,
respectively.
Statistical Analysis: Data were analyzed using the General Linear Model
procedure of
SAS (SAS, 1985). When a significant F statistic was noted by ANOVA, treatment
means were
compared using least square analysis variance.
Table 2 reports the results of this example.
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Table 2. Feed consumption, body weight gain, gain:feed ratio, hematocrit,
right
ventricular weight and ascites heart index of broilers to 14 days of age
fed diets with and without carnitine
Parameter Carnitine Level (ppm) ANOVA
P
0 200
Feed 358 8.4 352 8.8 0.609
Gain 261 3.0 265 3.1 0.343
Gain:feed 0.73 0.0 0.76 0.0 0.279
HCT (% 36.11 0.26 35.41 0.24 0.048
RV 0.21f0.005 0.20 0.006 0.043
AHR % 11.45 0.24 10.57 0.26 0.012
As shown in Table 2, carnitine supplementation in the broiler type chickens
had a positive
influence on the three primary indicators for ascites predisposition -
hematocrit (HCT) value,
right ventricle (RV) weight and acscites heart ratio (AHR). Hematocrit values
are the most direct
reflection of improved cardiac function, while right ventricle weight and
ascites heart ratio,
measured as the ratio of right ventricular mass to heart weight, facilitate
the assessment of the
cardiac traits associated with ascites. With the addition of 200 ppm of
carnitine in the basal diet,
hematocrit, right ventricle weight and ascites heart ratio were significantly
decreased (P<.05 ).
Further examples, conducted in the manner described above and reported below,
showed
a beneficial and significant lowering of hematcrit values for birds provided
with carnitine
supplemented diets at 12.5, 50 and 100 ppm carnitine.
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Table 3. Hematocrit values of broilers fed carnitine supplemented diets.
Carnitine Level HCT (%) ANOVA P
0 33.40
12.5 32.11 0.099
50 31.99 0.071
100 30.60 0.0004
By benefitting the cardiac traits associated with ascites, the above results
suggest that
dietary carnitine is effective at reducing the incidence of ascites in broiler
type poultry. The results
further suggest providing supplemental carnitine to poultry during periods of
high metabolic
demand, and, specifically, to broilers undergoing high rate tissue accretion,
such as genetically
engineered birds. From the experimental data and with knowledge of the field
it is reasonable to
extrapolate an effective range of supplementation of between 5 and 1000 ppm.
In the most preferred embodiment carnitine is administered to broiler type
poultry from
birth through harvest as a prophylactic measure to prevent the onset of
ascites. It is also
contemplated, however, that carnitine supplementation may be initiated as a
therapeutic remedy
upon the detection of symptoms indicating the onset of the ascites syndrome.
Such symptoms
may include an elevated blood hematocrit, elevated ascites heart ratio,
elevated ascites heart index
(a parameter measured as a ratio of right ventricle weight to total ventricle
weight and highly
correlated to ascites heart ratio), a bluish comb color and/or bird panting.
As used in this
paragraph, "elevated" simply means a value higher than that considered in the
field to be a normal
value.
While the invention has been described with a certain degree of particularity,
it is
understood that the invention is not limited to the embodiment(s) set for
herein for purposes of
exemplification, but is to be limited only by the scope of the attached claim
or claims, includin"'
the full range of equivalency to which each element thereof is entitled.
